Static and dynamic characteristics of membrane wings at low Reynolds number

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dc.contributor Lang, Amy W.
dc.contributor Olcmen, Semih M.
dc.contributor Mahmoodi, S. Nima
dc.contributor Su, Weihua
dc.contributor.advisor Hubner, James Paul Zhang, Zheng 2017-03-01T17:21:52Z 2017-03-01T17:21:52Z 2014
dc.identifier.other u0015_0000001_0001782
dc.identifier.other Zhang_alatus_0004D_11830
dc.description Electronic Thesis or Dissertation
dc.description.abstract To lessen the deterioration of fixed-wing aerodynamic performance associated with Reynolds numbers (Re) below 100,000, flexible membrane wing designs have been studied and proposed as an alternative for micro air vehicle (MAV) use. The beneficial effects of a flexible membrane can include higher lift, steeper lift-curve slope, delayed stall, gentle stall characteristics, and greater efficiency. These benefits have been attributed to both the time-averaged and dynamic deformation of the membrane. The background literature search shows that few investigations regarding membrane wings have focused on low aspect ratio (AR) wings (AR < 2) with a free (or unattached) trailing edge (TE), where the spanwise flow over the wing surface is dominant. Additionally, no study has looked at introducing membrane vibration at the leading edge (LE), which could potentially improve the aerodynamic performance by reducing the LE separation for the thin airfoil. Therefore, this work discusses the static and dynamic characteristics of a simplified membrane wing and airfoil configuration in the low Re flow (Re = 40,000 - 70,000). The global aerodynamic forces on the free TE membrane wing with varying wing AR, cell AR, and pre-strain level were measured. The result shows that the aerodynamic advantages of the flexible membrane are retained for the low AR wings. The optimal membrane cell AR is found to be approximately one. The comparison of the aerodynamic forces between the low AR membrane wings and the corresponding 3D- printed wings with the time-averaged deformation indicates the importance of membrane dynamic motion for the derived aerodynamic benefits. The effect of LE vibration was studied by performing wake velocity profile scans and aerodynamic load measurements on a spanwise tensioned, tip-bounded membrane cell. The LE vibration increased the lift coefficient in pre-stall region, but also resulted in a deeper wake, greater momentum loss, and less peak aerodynamic efficiency and power efficiency. Because the aerodynamic benefits by the membrane are attributed to the static and dynamic characteristics, the nondimensional deformation scaling and frequency scaling are proposed. For the stiff membrane, as the aerodynamic-induced strain is small, the membrane deflection can be reasonably predicted using a wave equation with a constant tension. For the flexible membrane, the trend of aerodynamic-induced strain with respect to dynamic pressure and angle-of-attack is qualitatively predicted using a catenary curve model. Compared with the traditional Strouhal scaling, the proposed nondimensional frequency scaling with the linear combination of applied strain and aerodynamic-induced strain better characterizes the fluid-structure interaction.
dc.format.extent 207 p.
dc.format.medium electronic
dc.format.mimetype application/pdf
dc.language English
dc.language.iso en_US
dc.publisher University of Alabama Libraries
dc.relation.ispartof The University of Alabama Electronic Theses and Dissertations
dc.relation.ispartof The University of Alabama Libraries Digital Collections
dc.relation.hasversion born digital
dc.rights All rights reserved by the author unless otherwise indicated.
dc.subject.other Aerospace engineering
dc.subject.other Mechanics
dc.title Static and dynamic characteristics of membrane wings at low Reynolds number
dc.type thesis
dc.type text University of Alabama. Dept. of Aerospace Engineering and Mechanics Aerospace Engineering The University of Alabama doctoral Ph.D.

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